Control of a transporter based on attitude

ABSTRACT

A transporter for transporting a load over a surface. The transporter includes a support platform for supporting the load. The support platform is characterized by a fore-aft axis, a lateral axis, and an orientation with respect to the surface, the orientation referred to as an attitude. At least one ground-contacting element is flexibly coupled to the support platform in such a manner that the attitude of the support platform is capable of variation. One or more ground-contacting elements are driven by a motorized drive arrangement. A sensor module generates a signal characterizing the attitude of the support platform. Based on the attitude, a controller commands the motorized drive arrangement.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 10/617,598, filed Jul. 11, 2003, which claims priority fromU.S. provisional patent application Ser. No. 60/395,589, filed Jul. 12,2002, both of which applications are hereby incorporated by referenceherein in their entirety.

TECHNICAL FIELD

The present invention pertains to transporters and methods fortransporting a load, which may be a living subject, and moreparticularly to controlling motion of a transporter.

BACKGROUND ART

A wide range of vehicles having a motorized drive arrangement are knownfor conveying various subjects, either for purposive locomotion or forrecreational purposes. The means used to command the motorized drivearrangement of these vehicles varies greatly. For example, an operatormay manipulate an accelerator pedal to control forward motion of anautomobile, while steering is typically performed using a steeringwheel. Or the motion of a sporting vehicle may be controlled by rockinga foot board upon which a user is balanced towards the front or rear tomechanically move a throttle cable, as described in U.S. Pat. No.4,790,548 (Francken). Based on the operator's physical attributes forexample, or the transporter's intended functionality, alternativemethods for controlling motion of a transporter may be desirable.

SUMMARY OF THE INVENTION

In a first embodiment of the invention there is provided a transporterfor transporting a load over a surface. The transporter includes asupport platform for supporting the load. The support platform ischaracterized by a fore-aft axis, a lateral axis, and an orientationwith respect to the surface, the orientation referred to as an attitude.At least one ground-contacting element, which is driven by a motorizeddrive arrangement, is coupled to the support platform in such a mannerthat the attitude of the support platform is capable of variation. Asensor module generates a signal characterizing the attitude of thesupport platform. Based on the attitude, a controller commands themotorized drive arrangement.

In accordance with related embodiments of the invention, one or moreground-contacting elements may be flexibly coupled to the supportplatform in such a manner that the attitude of the support platform iscapable of variation based on a position of a center of mass of the loadrelative to the at least one ground-contacting element.

The sensor module may include at least one distance sensor for measuringa distance characteristic of the attitude of the platform. The distancesensor may be selected from the group of distance sensors consisting ofan ultrasonic distance sensor, an acoustic distance sensor, a radardistance sensor, optical distance sensor, and a contact sensor, such asa whisker(s). The at least one distance sensor may sense the distancebetween a fiducial point on the platform and a position on the surfacedisposed at a specified angle with respect to the support platform. Inother embodiments, the transporter may include a first component thatremains in a substantially fixed vertical position relative to thesurface, wherein the at least one distance sensor senses the distancebetween a fiducial point on the platform and the first component. One ormore ground contacting elements may include a wheel having an axle, andthe first component is fixed relative to the axle. Alternatively, andnot meant to be limiting, one or more ground contacting elements mayinclude a wheel supported by a frame, and the first component is fixedrelative to the frame.

In accordance with other related embodiments of the invention, theattitude of the support platform is capable of variation based at leaston a signal generated by a remote control device. The transporter mayinclude a powered strut coupled to the platform, the powered strutcapable of varying the attitude of the support platform based at leaston the signal generated by the remote control device. The transportermay further include a user interface, wherein the attitude of thesupport platform is capable of variation based on a signal generated bythe user interface. The controller may command motion of the transporterin the fore-aft plane and/or the lateral plane.

In accordance with another embodiment of the invention, a method forcontrolling a transporter having a support platform for supporting aload is presented. The support platform is characterized by an attitudewith respect to the surface. The transporter includes at least oneground contacting elements flexibly coupled to the support platform insuch a manner that the attitude of the platform is capable of variation.The transporter also includes a motorized drive arrangement for drivingthe at least one ground contacting elements. The method includesgenerating a signal characterizing an attitude of the support platform.The motorized drive arrangement is commanded based at least on theattitude.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the invention will be more readily understoodby reference to the following detailed description, taken with referenceto the accompanying drawings, in which:

FIG. 1 depicts one embodiment of a human transporter, lacking a distinctuser input device, to which the present invention may advantageously beapplied;

FIG. 2 is a side view of a transporter, in accordance with oneembodiment of the invention;

FIG. 3 is an expanded side view of a transporter, in accordance with oneembodiment of the invention;

FIG. 4 is a side view of a transporter, in accordance with oneembodiment of the invention; and

FIG. 5 is a block diagram of a controller of a transporter, inaccordance with one embodiment of the invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

In accordance with one embodiment of the invention, FIG. 1 shows atransporter, 1 lacking a distinct input device, to which the presentinvention may advantageously be applied. Transporter 1 is described indetail in U.S. Pat. No. 6,302,230, which is incorporated herein byreference in its entirety. Transporter 1 includes a support platform 11for supporting a load, which may be a living subject 9, over the groundor other surface, such as a floor, which may be referred to hereingenerally as “ground”. A subject, for example, may stand or sit onsupport platform 11. Attached to support platform 11 may be a handlebar12 that can be gripped when riding transporter 1.

One or more ground-contacting elements 2, 7 provide contact betweensupport platform 11 and the ground. Ground-contacting elements 2, 7 mayinclude, but are not limited to, arcuate members, tracks, treads, andwheels (hereinafter the term “wheel” will be used in the specificationto refer to any such ground-contacting element without limitation).While the transporter 1 depicted in FIG. 1 lacks stability in itsoperating position unless subject to controlled balancing, theapplication of the present invention is specifically not limited totransporters of that sort and embodiments of the present invention mayadvantageously be applied to statically stable transporters as well.

Support platform 11 may be flexibly coupled to the wheels 2, 7 byvarious means known in the art, for example, a pivot mechanism, springs,or pneumatic pistons. In other embodiments, the wheels 2, 7 may havesome compliance and serve the function of a spring. For purposes of thepresent description, platform 11 may be characterized by a fore-aftaxis, a lateral axis, and an orientation with respect to the surface,which is referred to herein as an attitude. The fore-aft axis, X-X, isperpendicular to the wheel axis, while the lateral axis, Y-Y, isparallel to the axis of the wheels. Directions parallel to the axes X-Xand Y-Y are called the fore-aft and lateral directions respectively.

Referring now to FIG. 2, which shows a transporter 10 in accordance withone embodiment of the invention, the attitude of support platform 11may, for example, be capable of variation based on a position of acenter of mass of the load relative to one or more wheels 13, 14.Alternatively, transporter 10 may include a power strut or othermechanism capable of altering the attitude of the support platform 11.The power strut may be controlled by a user interface located ontransporter 10, such as a joystick or a rotatable potentiometer locatedon handlebar 12. In other embodiments, the power strut may also becontrolled by a remote control device, such as, but not limited to, aninfrared or radio controlled remote control device.

The motion of transporter 10 is based, at least in part, on the attitudeof the support platform 11. To determine the attitude of the supportplatform 11, transporter 10 includes a sensor module. Sensor module mayinclude at least one distance sensor 17, 18 for measuring a distancecharacteristic of the attitude of the support platform 11. The distancemeasured may be, for example, the distance between a fiducial point onthe support platform 11 and a surface 19, or alternatively, anothercomponent on transporter 10. A plurality of distances measured by thesensor module may be combined to generate at least one signalcharacteristic of the platform attitude.

Attitude/distance sensor may be one of many sensor types, such as, forexample, an ultrasonic, optical, acoustic or radar sensor wherein asignal generated by a source is reflected back by a surface to a sensorreceiver. The distance from the sensor to the surface can then becalculated based on the time (or phase) difference between when thesignal was generated and when the reflected signal was received.Triangulation may be performed. In other embodiments, distance sensorcan be a contact sensor(s) such as, without limitation, a whisker(s).For example, a plurality of whiskers, each having a predetermined lengthmay be utilized, with distance determined based on which whisker bendsor is otherwise activated when making contact with the surface. A singlewhisker may be utilized with distance determined based, at least onpart, on the bending angle of the whisker.

Referring to FIG. 2, distance sensors 17, 18 sense the distance betweena fiducial point on the platform and a position on the surface that isdisposed at a specified angle 3, 4, with respect to the supportplatform. First distance sensor 17 is located at the front (fore) ofplatform 11 and senses a first distance 5 between platform 11 andsurface 19. Second distance sensor 17 is located at the back (aft) ofplatform 11 and senses a second distance 6 between platform 11 andsurface 19. By comparing distances 5 and 6, a signal indicative of anattitude of the platform 11, and more specifically, the inclination ofthe platform 11 in the fore-aft plane with respect to the surface 19,can be determined.

In another embodiment, at least one distance sensor 22 may sense thedistance between a fiducial point on the transporter platform 11 and afirst component 23 that remains in a substantially fixed verticalposition relative to the surface 19, as shown in the expanded view of atransporter in FIG. 3. First component 23 may be, for example, a wheelaxle 23 or a frame used to support the at least one wheel 14. In variousembodiments, first component 23 may include a reflector for reflectingthe signal generated by distance sensor 22.

FIG. 4 shows a transporter 60 that includes a first support platform 69and a second support platform 61, in accordance with one embodiment ofthe invention. At least one wheel 63 and 64 provides contact between thefirst support platform 69 and the ground. Second support platform 61 iscoupled to the first support platform 69 such that the second supportplatform 61 can tilt in the fore-aft plane based, for example, on aposition of a center of mass of the loaded second support platform 61.Second support platform 61 may be tiltably attached to the first supportplatform 69 using, without limitation, springs 65 and 66 and/or a pivotmechanism 68. Similar to above-described embodiments, based on thetilting of the second support platform 61, at least one sensor 67 and 70generates a signal indicative of the attitude of the second supportplatform 61. Attached to the first support platform 69 or second supportplatform 61 may be a handlebar 62 that can be gripped while operatingthe transporter 60.

A controller receives the signal characteristic of the attitude from thesensor module. Based at least on this signal, the controller implementsa control algorithm to command a motorized drive arrangement so as todrive the at least one wheel. The controller may also respond tocommands from other operator interfaces, such as a joystick or dialattached, for example, to handlebar.

FIG. 5 shows a controller 30 for controlling the motorized drive of thetransporter, in accordance with one embodiment of the invention.Controller 30 receives an input characteristic of platform attitude fromsensor module 34. Based at least on the input from the sensor module,controller 30 commands at least one motorized drive 35, 36. Controller30 also interfaces with a user interface 31 and a wheel rotation sensor33. User interface 31 may include, among other things, controls forturning the controller 30 on or off. When the controller 30 is turnedoff, the at least one wheel of the transporter may be free to move, suchthat the transporter acts as a typical push scooter. User interface 31may also control a locking mechanism 32 for locking the at least onewheel.

The controller 30 includes a control algorithm to determine the amountof torque to be applied to the at least one wheel based on the sensedattitude of the support platform. The control algorithm may beconfigured either in design of the system or in real time, on the basisof current operating mode and operating conditions as well aspreferences of the user. Controller may implement the control algorithmby using a control loop. The operation of control loops is well known inthe art of electromechanical engineering and is outlined, for example,in Fraser & Milne, Electro-Mechanical Engineering, IEEE Press (1994),particularly in Chapter 11, “Principles of Continuous Control” which isincorporated herein by reference.

As an example, and not meant to be limiting, the control algorithm maytake the form:Torque Command to Wheel=K[θ+O]

where

-   -   K=gain,    -   θ=support platform attitude, and    -   O=offset.

The support platform attitude, θ, may be in the form of an error termdefined as the desired support platform attitude minus the measuredsupport platform attitude. The gain, K, may be a predetermined constant,or may be entered/adjusted by the operator through user interface 31.Responsiveness of the transporter to attitude changes can be governed byK. For example, if K is increased, a rider will perceive a stifferresponse in that a small change in platform attitude will result in alarge torque command. Offset, O, may be incorporated into the controlalgorithm to govern the torque applied to the motorized drive, either inaddition to, or separate from, the direct effect of θ. Thus, forexample, the user may provide an input by means of a user interface ofany sort, the input being treated by the control system equivalently toa change, for example, in platform attitude.

Thus, referring back to FIG. 2, motion of the transporter 10 may becontrolled by a subject changing the attitude of the platform 11. Thischange in attitude is reflected by distances 5, 6 sensed by the sensormodule. Depending on the control algorithm, an initial change inattitude, such that first distance 5 is less than second distance 6, mayresult in positive torque being applied to one or more wheels 23, 24,causing the wheels 23, 24 to move forward. Likewise, an initial changein the attitude, such that first distance 5 is greater than seconddistance 6 may result in a negative torque applied to one or more wheels23, 24, causing the wheels 23, 24 to move in the aft direction. If thesubject then remains in his changed position on the platform such thatthe platform attitude remains the same, the motor will continue totorque at approximately the same rate.

In various embodiments of the invention, the sensor module may sensechanges in platform attitude in addition to, or instead of inclinationof support platform in the fore-aft plane. For example, sensor modulemay provide an attitude signal indicative of inclination of the supportplatform in the lateral plane relative to the surface. This may beaccomplished by the use of two laterally disposed distance sensors.Changes in the angle of inclination of the support platform in thelateral plane can then be used either separately or in combination withother attitude changes to control motion of the transporter. Forexample, changes in the angle of inclination in the fore-aft plane canbe used to control fore-aft motion, while changes in the angle ofinclination in the lateral plane can be used to control steering of thetransporter.

Steering may be accomplished, in an embodiment having at least twolaterally disposed wheels (i.e., a left and and right wheel), byproviding separate motors for left and right wheels. Torque desired forthe left motor and the torque desired from the right motor can becalculated separately. Additionally, tracking both the left wheel motionand the right wheel motion permits adjustments to be made, as known topersons of ordinary skill in the control arts, to prevent unwantedturning of the vehicle and to account for performance variations betweenthe two motors.

The described embodiments of the invention are intended to be merelyexemplary and numerous variations and modifications will be apparent tothose skilled in the art. All such variations and modifications areintended to be within the scope of the present invention as defined inthe appended claims.

What is claimed is:
 1. A transporter for transporting a load over asurface, the transporter comprising: a support platform for supportingthe load, the support platform characterized by a fore-aft axis and alateral axis; at least one ground-contacting element coupled to thesupport platform in such a manner that the orientation of the supportplatform with respect to the surface beneath and in contact with the atleast one ground-contacting elements is capable of variation, theorientation referred to as an attitude; a motorized drive arrangementfor driving the at least one ground-contacting elements; a sensor modulefor generating a signal characterizing the attitude of the supportplatform; and a controller for commanding the motorized drivearrangement to apply a torque to one or more of the ground-contactingelements as a function of the attitude of the support platform basedupon the signal generated by the sensor module.
 2. The transporteraccording to claim 1, wherein one or more ground-contacting elements areflexibly coupled to the support platform in such a manner that theattitude of the support platform is capable of variation based on aposition of a center of mass of the load relative to the at least oneground-contacting element.
 3. The transporter according to claim 1,further including a first component that remains in a substantiallyfixed vertical position relative to the surface, wherein one or moreground contacting elements include a wheel having an axle, and the firstcomponent is fixed relative to the axle and wherein the sensor modulesenses the distance between a fiducial point on the platform and thefirst component.
 4. The transporter according to claim 3, wherein one ormore ground contacting elements include a wheel supported by a frame,and the first component is fixed relative to the frame.
 5. Thetransporter according to claim 1, wherein the attitude of the supportplatform is capable of variation based at least on a signal generated bya remote control device.
 6. The transporter according to claim 5,further including a powered strut coupled to the platform, the poweredstrut capable of varying the attitude of the support platform based atleast on the signal generated by the remote control device.
 7. Thetransporter according to claim 1, further comprising a user interface,wherein the attitude of the support platform is capable of variationbased on a signal generated by the user interface.
 8. The transporteraccording to claim 1, wherein the controller commands motion in thefore-aft plane.
 9. The transporter according to claim 1, wherein thecontroller commands motion in the lateral plane.
 10. A method forcontrolling a transporter having a support platform for supporting aload, the support platform characterized by an attitude with respect toa surface beneath the transporter, the transporter including at leastone ground contacting elements flexibly coupled to the support platformin such a manner that the attitude of the platform is capable ofvariation, the transporter further including a motorized drivearrangement for driving the at least one ground contacting element, themethod comprising: generating a signal characterizing an attitude of thesupport platform; and commanding the motorized drive arrangement toapply a torque to one or more of the ground-contacting elements as afunction of the attitude based upon the signal.
 11. A method accordingto claim 10, wherein generating the signal includes measuring a distancebetween a fiducial point on the platform and a position on the surfacedisposed at a specified angle.
 12. A method according to claim 10,wherein generating the signal includes measuring the distance between afiducial point on the platform and a component on the transporter thatremains in a substantially fixed position relative to the surface.
 13. Amethod according to claim 10, further comprising altering the attitudeof the support platform by changing a position of a center-of-mass ofthe load relative to the at least one ground contacting element.
 14. Amethod according to claim 10, further comprising altering the attitudeof the support platform based at least on a signal generated by a userinterface of the transporter.
 15. A method according to claim 10,further comprising altering the attitude of the support platform basedat least on a signal generated by a remote control device.